Synthetical applications of activated metal catalysts. XXVI. The formation of biaryls from azahydrocarbons under the influence of rhodium-on-carbon

Abstract

The action of degassed rhodium-on-carbon on 14 azahydrocarbons has been examined. 2,2'-Biaryls are formed in 15-50% yield from quinoline, 6-methyl-quinoline, 7-methylquinoline, 4-phenylpyridine, and 4-benzylpyridine at their boiling points, and from benzo[f]quinoline at 320-330º. By-products formed from quinoline include 2,3'-biquinolyl, two triquinolyls, and the products of hydrogenolysis previously obtained from experiments with quinoline and degassed Raney nickel. The methylquinolines undergo demethylation; methylation occurs at the 2- and 4-positions in quinoline. 2-Methylquinoline forms inter alia bis(2-quinolyl)methane, tris(2-quinolyl)methane, and 1,2-bis(2-quinolyl)ethane. The results obtained with rhodium-on-carbon are compared with those obtained with degassed Raney nickel.